The present invention relates to a magnetic disk unit which records and reproduces data in/from a disk-shaped magnetic recording medium by employing a magnetic head and, more particularly, to a magnetic disk unit which performs positioning of the magnetic head in a short amount of time.
A disk-shaped magnetic recording medium generally has a reference track provided in its innermost circumference and data tracks formed outside the reference track toward the outer circumference of the disk. Data are written in or read from the data tracks by a magnetic head which moves perpendicularly to the circumference direction of the magnetic recording medium. Further, there is a disk-shaped magnetic recording medium on which an optical groove is formed adjoining to each data track. In this case, the magnetic disk unit moves the magnetic head and sets the magnetic head on a track on the basis of the optical groove to thereby read or write data from/in the data track by the magnetic head. The optical groove as a reference for a set-on-track and the data track are usually located apart from each other by several tens of tracks.
To make it possible to exchange such disk-shaped magnetic recording medium among plural magnetic disk units, positioning of the magnetic head should be performed. When the disk-shaped magnetic recording medium has a high track density, accuracy is required for the positioning of the magnetic head.
A conventional method of positioning a magnetic head in a magnetic disk unit as described above is disclosed in Japanese Published Patent Application No. Hei. 2-187969, which discloses that every time a disk-shaped magnetic recording medium is set in the magnetic disk unit, the magnetic disk unit moves the magnetic head to a reference track provided on each disk-shaped magnetic recording medium as an initial operation, and sets an absolute track-zero position from the reference track, thereby performing accurate positioning of the magnetic head.
However, to move the magnetic head to the reference track by the conventional magnetic head positioning method, an operation of performing coarse adjustment which roughly moves the magnetic head to the reference track at the innermost circumference of the recording medium and then performing fine adjustment which slightly moves the magnetic head in the vicinity of the reference track is required. Further, since the conventional magnetic disk unit has an error in a write position of the reference track on the recording medium, an error caused by the accuracy of the coarse adjustment, and an error in a position of the magnetic head with respect to an optical servo due to temperature expansion, a positional range of reference track detection that is performed at the fine adjustment of the magnetic head must be set widely from several tracks to several tens of tracks, which results in a long period of time to position the magnetic head.
The present invention is made to solve the above-mentioned problems. The object of the present invention is therefore to provide a magnetic disk unit which can perform positioning of a magnetic head in a short time.
According to a first aspect of the present invention, there is provided a magnetic disk unit which rotates a disks-shaped magnetic recording medium having a reference track and plural data tracks with a motor, which generates an index signal at a predetermined position, and records or reproduces data by employing a magnetic head. The magnetic disk unit of the first aspect comprises a head moving means (unit) for slightly moving the magnetic head in the direction of the radius of the disk-shaped magnetic recording medium in a predetermined unit of a distance that is shorter than the data track width. The magnetic disk unit also comprises a reproduction output amplitude measuring means (unit) for measuring the reproduction output amplitude of a signal that is read from a data track by the magnetic head each time the index signal is generated. The magnetic disk unit further comprises a CPU which obtains a position where the reproduction output amplitude has the maximum value based on the reproduction output amplitude measured by the reproduction output amplitude measuring means and the number of head movements of the magnetic head as moved by the head moving means so as to perform control of data track positioning of the magnetic head on the data track.
Therefore, data track positioning of the magnetic head in each data track on the disk-shaped magnetic recording medium having a reference track and plural data tracks can be performed accurately in a short amount of time.
According to a second aspect of the present invention, there is provided a magnetic disk unit which rotates a disk-shaped magnetic recording medium having a reference track, plural data tracks, and optical grooves sandwiched between the respective data tracks with a motor, which generates an index signal at a predetermined position, and which records or reproduces data by employing a magnetic head. The magnetic disk unit of the second aspect comprises a head moving means (unit) for slightly moving the magnetic head in the direction of the radius of the disk-shaped magnetic recording medium in a predetermined unit of a distance that is shorter than the data track width. The magnetic disk unit of the second aspect also comprises a reproduction output amplitude measuring means (unit) for measuring the reproduction output amplitude of a signal that is read from a data track by the magnetic head each time the index signal is generated. The magnetic disk unit of the second aspect further comprises a CPU which obtains a position where the reproduction output amplitude has the maximum value based on the reproduction output amplitude that is measured by the reproduction output amplitude measuring means and the number of head movements of the magnetic head as moved by the head moving means so as to perform control of data track positioning of the magnetic head on the data track.
Therefore, data track positioning of the magnetic head in each data track on the disk-shaped magnetic recording medium having a reference track, plural data tracks, and optical grooves sandwiched between the respective data tracks can be performed accurately in a short amount of time.
According to a third aspect of the present invention, in accordance with the magnetic disk unit of the first and second aspects, there is further provided a track position detecting means (unit) for detecting the data track position from the signal that is read from the data track by the magnetic head. Further, according to the third aspect the CPU calculates a relative positional difference between the data track position that is detected by the track position detecting means and the reference track position, and performs control of reference track positioning of the magnetic head on the basis of the calculation result.
Therefore, accurate movement is possible for coarse adjustment in reference track positioning of the magnetic head, whereby the positional range of reference track detection at fine adjustment is narrowed, thereby resulting in a short-time and accurate reference track positioning.
According to a fourth aspect of the present invention, in accordance with the magnetic disk unit of the first or second aspects, the data track positioning control by the CPU holds the head moving cycle number, the value of the reproduction output amplitude which is measured by the reproduction output amplitude measuring means at the head moving cycle number each time the index signal is generated, and the maximum reproduction output amplitude cycle number which is the moving cycle number having a larger reproduction output amplitude when compared between the measured reproduction output amplitude and the reproduction output amplitude at the immediately previous moving cycle number. After performing processing corresponding to a predetermined number of moving cycle numbers by the CPU, a position of the maximum reproduction output amplitude on the data track is obtained on the basis of the maximum reproduction output amplitude cycle number, and the obtained position is set as a data track position of the magnetic head on the data track.
Therefore, data track positioning of the magnetic head can be performed accurately in a short amount of time so as to reproduce data from the data track without performing reference track positioning.
According to a fifth aspect of the present invention, in accordance with the magnetic disk unit of the fourth aspect, there is further provided a track position detecting means (unit) for detecting the data track position from the signal that is read from the data track by the magnetic head. Further, according to the fifth aspect, the CPU calculates a relative positional difference between the data track position that is detected by the track position detecting means and the reference track position, and performs a control of reference track positioning of the magnetic head on the basis of the calculation result.
Therefore, data track positioning of the magnetic head is performed in a short amount of time so as to reproduce data from the data track without performing reference track positioning and, further, accurate movement is possible for coarse adjustment in reference track positioning of the magnetic head, whereby the positional range of reference track detection at fine adjustment is narrowed, thereby resulting in a short-time and accurate reference track positioning.